Droxidopa is a pharmaceutical agent mainly used for improving frozen gait and orthostatic dizziness in patients with Parkinson's syndrome, as well as for treating orthostatic hypotension in dialysis patients. Production of droxidopa tablet has been difficult since it is colored when admixed with various additives such as excipients, binders and the like, and under humidity. As droxidopa preparation, therefore, only dry capsules and fine granules obtained by granulation with an organic solvent without using water are currently commercially available, and capsules are prescribed for most patients.
According to the results of a survey on a dosage form easy to take for patients (easy administrability search), the dosage form easiest to take is tablet, and many patients are known to feel uncomfortable for capsule because it sticks to the throat and the like. Particularly, in view of the fact that many of the patients affected with Parkinson's syndrome and the like, who take droxidopa, are aged individuals, and the proportion of patients with decreased swallowing ability due to the progression of the disease is high, the development of a tablet with easy administrability, particularly an easy-to-take tablet rapidly disintegrated in the oral cavity, which is promptly disintegrated in the oral cavity and does not cause uncomfortableness, has been desired rather than capsules.
As a tablet containing droxidopa, which is rapid disintegrating in the oral cavity, for example, patent reference 1 discloses a rapid-disintegrating tablet containing polyvinyl alcohol, and recites droxidopa as a usable efficacy component. In addition, patent reference 2 discloses a tablet that is rapidly disintegrated in the oral cavity, which characteristically contains starch as an aqueous excipient (binder), where droxidopa is recited as an efficacy component.
However, actual production of a tablet containing droxidopa has not been known.    patent reference 1: WO01/064190    patent reference 2: WO00/47233    non-patent reference 1: Byoin Yakugaku Vol. 11, No. 3, 284-292 (1985)